Euphorbia (spurge) is a very large and diverse genus of flowering plants in the spurge family (Euphorbiaceae). Sometimes in ordinary English, "euphorbia" is used to refer to the entire Euphorbiaceae family (as the type genus), not just to members of the genus. Some euphorbias are commercially widely available, such as poinsettias at Christmas. Some are commonly cultivated as ornamentals, or collected and highly valued for the aesthetic appearance of their unique floral structures, such as the crown of thorns plant. Euphorbias from the deserts of Southern Africa and Madagascar have evolved physical characteristics and forms similar to cacti of North and South America, so they (along with various other kinds of plants) are often incorrectly referred to as "cacti". Some are used as ornamental